1. Field of the Invention
The present invention relates to a dynamic vibration absorbing apparatus for an optical disk drive, and particularly to a dynamic vibration absorbing apparatus that absorbs vibration due to an unbalanced disk at high rotational speeds in the optical disk drive.
2. Description of the Prior Art
Since optical media technology has rapidly improved in recent years, various kinds of optical disk drives are involved in applications as computer peripherals. Presently, most commercially available optical disk drives are made to operate with the rotational speed of their spindle motor over 10000 rpm.
However, it is possible that the optical disk loaded into an optical disk drive may be eccentric. When both the eccentric disk and the spindle motor of the optical disk drive is operated at a relatively high rotational speed, centrifugal force due to imbalance of the eccentric disk increases and may lead to vibration or noise. The vibration creates instability that impairs the optical pickup head of the optical disk drive, so that error occurs in data readout, and the noise can be annoying or even hazardous to the user. Furthermore, reading data from unstable optical disk may also result in the deterioration of the performance of the optical disk drive. Accordingly, elimination of vibration and noise at high rotational speeds is a major concern for manufacturers.
Conventionally, there are three methods to reduce vibration and noise in optical disk drives at high rotational speeds due to imbalance of the optical disk.
In one conventional method, extra weight is applied to the data readout device (i.e. the “mecha”) of the optical disk drive. This method directly increases the weight of the optical disk drive and attempts to reduce vibration. Unfortunately, vibration cannot be significantly reduced.
Another method of reducing the vibration of the optical disk drive uses an additional auto-balancing system in the optical disk drive. In the auto-balancing system, a balancing component is applied to balance the eccentric disk. In practical use, however, this method is limited by the manufacturing factors such as concentricity or roughness, and it is not possible to apply a specific balancing component to deal with vibration and noise due to various types of eccentric disks. Obviously, many specific components need to accomplish this and cause more cost.
The third method applies a dynamic vibration absorber in accordance with vibration theory to the optical disk drive. The dynamic vibration absorber includes an elastic block, i.e. an absorber, provided either above or under the base of the optical disk drive. According to the vibration theory, when the elastic block has a natural frequency that is equal to the harmonic frequency of the base in vibration, the base has a displacement of zero. That is, the elastic block absorbs vibration due to the base.
FIG. 1 shows a conventional dynamic vibration absorber commonly used in the optical disk drive. In FIG. 1, a plurality of dampers 12a is elastic members, and is provided between the block 10a and the base 11a. A plurality of vibration absorbing dampers 13a is damping components and provided between the base 11a and the base supporting device. In this case, the dynamic vibration absorber significantly reduces vibration of the optical disk drive.
However, in the conventional dynamic vibration absorber, the dampers 12a and the vibration absorbing dampers 13a are different shapes and of different materials, which is not preferable in consideration of cost and manufacture of the optical disk drive. Consequently, there is a need to develop a dynamic vibration absorbing apparatus for the optical disk drive without the above-mentioned disadvantages.